According to Osho, Aum was chosen to signify the seventh plane because it is beyond meaning: composed only of the three primal sounds a‑u‑m, which by themselves carry no concept. To prevent conceptual capture, it’s rendered as a pictorial symbol of three parts. Heard as an inner hum in thoughtless stillness, it functions as a doorway-question mark pointing to the source beyond language.
Aum is a meaning-free sound-picture made from basic sounds that helps stop thinking and guides you to the silent source of everything.
From the Discourses
Passages where Osho speaks to this question — each links to the complete discourse.
What are the distinctive characteristics of aum for which it has been chosen to represent the seventh plane?
Now as I said before, each word has a pattern of its own. When we use a certain word a particular pattern forms within the mind. If someone meditates on aum, when it resounds on the fourth plane the corresponding picture will begin to manifest within. This is how all seed mantras were discovered. When the resonance of a particular chakra is caught by a meditator in meditation, the seed mantra of that chakra is revealed. This is how these seed mantras have been formed, and aum is the ultimate seed. It is not the seed of any particular chakra; rather, it is the symbol of the seventh which is the infinite or the eternal. So in this way the word aum was hit upon. And when it tallied with the experiences of thousands of seekers who gave it their approval, this word was accepted. It did not come into…
Osho, why was Om chosen as a symbol? What are its special features?
There are two reasons Om was chosen. First, the search was for a word that has no meaning, to which you cannot attach meaning; because if you do, it falls on this side of the fifth. A word was needed that, in one sense, is meaningless. Or say: beyond meaning. Both are the same. All our words are meaningful. We coin words precisely so they bear meaning. If there is no meaning, what need is there for a word? We make words to speak, and the purpose of speaking is that I may convey something to you; when I speak, there should be a hint of meaning for you. When people returned from the seventh—or went to the seventh—they felt: whatever word we make, if it carries meaning, it will immediately fall before the fifth body. The dictionary will write out its meaning; people will read and think they have…
In the context of the seventh body, you talked about aum yesterday. There is still a small question on the same subject. Which chakras do a, u and m influence, and how is this helpful to the meditator?
The greater possibility with chantings and mantras is that your mind with its tendency to dream will at once, by its very mechanical process, fall into dreaming. But if you are fully awake and witnessing inside, observing the sound of aum without merging into it, without losing yourself in it, then it could do the same work as repeating "Who am I?" -- which I advocate. Now if you ask "Who am I?" in a sleepy state and are not a witness, the same error can take place here and you will merely be dreaming. But the possibility of this happening with "Who am I?" is less than with the repetition of aum, and there is a reason for it. With aum there is no question asked; it is only a gentle touch. With "Who am I?" there is a question, not a mere pat. There is a question mark…
Osho, yesterday you spoke a little about Om in reference to the seventh body. In that context, a small question is: which chakras are affected by the vibrations of A, U, and M, and how might they be used by a seeker? What is the relation of these chakric effects to the seventh chakra?
Even so, my constant view remains that Om is to be used only as a symbol, not as a practice. Other devices can be found for practice. Such a sacred word as Om should not be profaned by using it as a means. Therefore many misunderstand me. Many people come to me and say, “If we chant Om, why do you forbid it?” Perhaps it seems to them that I am an enemy of Om. But I know that they are the enemies; because such a supremely sacred word should not be used as a means. In truth, it is not a word meant to be spoken by our tongue. In truth, it is not to be uttered by our body. It begins where the tongue loses meaning and the body becomes useless; there is its resonance. And we do not make that resonance—it happens; it is known; it is…
Soyam atmadhyaksaram, onkaro'dhimatram pada matra, matras ca pada akara ukaro makara iti. Jagarita-sthano vaisvanaro'karah prathama matra apter adimattva dva, apnoti ha vai. Sarvan kaman, adis ca bhavati, yaevam veda.
SVAPNA-STHANAS TAIJASA UKARO DVITIYA MATRA UTKARSADU- BHAYATVAD VA UTKARSATI HA VAI JNANA-SANTATI, SAMANAS CA BHAVATI NASYABRAHMA-VIT KULE BHAVATI YA EVAM VEDA. SUSUPTA-STHANAH PRAJNO MAKARAS TRTIYA MATRA MITER APITER BA, MINOTI HA VA IDAM SARVAM, APITAS CA BHAVATI YA EVAM VEDA. AMATRAS CATURTHO'VYAVAHARYAH PRAPANCOPASAMAH, SIVODVAITA EVAM OMKARA ATMAIVA SAMVISTYATMANATMANAM YA EVAM VEDA, YA EVAM VEDA. THIS PURE SELF AND AUM ARE AS ONE; AND THE DIFFERENT QUARTERS OF THE SELF CORRESPOND TO AUM AND ITS SOUNDS, A-U-M. EXPERIENCE OF THE OUTER WORLD CORRESPONDS TO A, THE FIRST SOUND. THIS INITIATES ACTION AND ACHIEVEMENT. WHOEVER AWAKENS TO THIS ACTS IN FREEDOM AND ACHIEVES SUCCESS. EXPERIENCE OF THE INNER WORLD CORRESPONDS TO U, THE SECOND SOUND. THIS INITIATES UPHOLDING AND UNIFICATION. WHOEVER AWAKENS TO THIS UPHOLDS THE TRADITION OF KNOWLEDGE AND UNIFIES THE DIVERSITIES OF LIFE. EVERYTHING THAT COMES ALONG SPEAKS TO HIM OF BRAHMAN. THE STATE OF DREAMLESS SLEEP CORRESPONDS TO M,…